Electric motor



July 8, 1930. w, STUMPF 1,770,113

ELECTRIC IOTOR Filed June 28, 1926 .2 Sheets-Sheet 1 July 8, 1930. wSTUMPF 1,770,113

ELECTRIC .IOTOR Filed June 28. 1926 2 Sheets-Sheet 2 ZZZ Patented July8, 1930 UNITED STATES PATENT o1=1=1c1-:

WALTR STUHPI', OI BALTIMORE COUNTY, MARYLAND, ASSIGNOR TO THE BLACK &DECKER MANUFACTURING COMPANY, OF TOWSON, MARYLAND, A CORPORATION 01IARYLAN D ELECTRIC MOTOR Application filed June 28,

In themanufacture of portable electric tools the expense incident tomachming the same with a sufficient degree of accuracy torovide for thepositioning of the armature Bearings, which, on account of the highspeeds attained, must be practically frlctionless andftherefore,located, and aligned with exactness, has been an important item. It hasalso been difficult to provide for taking up the wear in the bearingsresulting in both end play and side play. To overcome the difficultythus encountered one of the bearings is mounted to slide in thedirection of the axis, the wear and plati bein taken up by a springwhich presses e sli ing bearing toward the fixed bearing, prefera lyacting on the outer race. g

The present invention relates to the ositioning means and also tovarious detai s of the means for positioning the bearing and taking upthe play as aforesaid.

An important ditnculty has been due to the tendency of the service menin re-assembling after removing the armature to leave out parts of thebearing supporting and pos1- tionin elements, which ordinarily drop outwith t e shaft. A feature of the invention relates to securing thespring to the spring cup or washer or to both the cup and the housing sothat in the first instance the spring cannot be easily removed from thecup and 'the combined parts are not apt to be overlooked, and in thesecond instance neither the s ring nor the cup can be easily removedfrom tile casing or housing.

In the accompanying drawings I have illustrated so much of a portablerotary electric tool of the drill type as is considered necessary to afull comprehension of my invention and the manner of applying the same.I

In the drawings:

Figure 1 is a vertical central section of a portable electric tool, thehandle being shown in elevation and the s indle and lower portion of thegear casing ing broken away for convenience of illustration.

Figure 2 is an elevation of the spindle and lower portion of the gearcasing below the broken line in Figure 1. 1-

Figure 3 is a section taken on the line of the 1926. Serial No. 118,971.

axis through the rear or upper motor bearing and adjacent portion of themotor housing.

Figure 4 is an end elevation or top plan of the same looking from theright in F igure 3.

Figure 5 is an axial section through the spring cup and spring.

Figure 6 is a view of the the right in Figure 5.

Referring to the. drawings by numerals, each of which is used toindicate the same or similar parts in the different figures, theillustration includes an electric drill or similar portable rotaryelectric tool 1, comprising a motor housing 2 enclosing motor 3 andhaving rigidly connected thereto at one end a handle 4 and at the otherend gear casing 5 enclosing reducin gearing 6 by means of which thespindle is rotatlvely connected to and driven by and from the motor 3.The motor is provided with a rotating armature 9 mounted on a shaft 10rotating in a fixed bearing 11 located by shoulder 12 at one end, and atthe other end in a bearing 14 mounted in a suitable recess or chamber 15formed in the end of the housing for this purpose, the said bearinghaving a sliding relation with said housing, or more particularly thebushing 16 therein which carries the outer race 17 of the hearing, whichis shown as a ball bearing. The inner race 18 is secured to the shaft,being either pressed or sWeated on the shaft and the tendency to endplay of the shaft and to similar motion in the axial direction of thebearing is taken up by means of a spring 19 which, as shown, is a spiralspring, bearing at one end on the end or rear wall 20 of the chamber 15and in the other direction on the bottom of the spring cup 21 whichpreferably engages the outer race 17 of the open ended bearing shown.Neither the ty e of bearing nor the exact arrangement (i;- scribed isessential to the broadest conception of the invention.

It is obvious that the inner race bein grooved at '22 to receive theballs 24 andthe inner race itself being secured to the shaft, theouterrace being grooved at 25 on the outer or upper side of same looking fromthe balls, the end play is conveniently taken likewise shouldered or aup by the spring pressure against the outer race.

Where an open bearing is used, as in the form illustrated, the outerrace is made with a cylindrical surface 26 which extends toward thelower or inner end of the bearing for a very short distance which may beconveniently about one millimeter. This provides for a slight degree ofmotion of the outer race relatively to the rest of the bearing with outinjury to the bearing. The motion of the outer race is limited to thelength of the cylindrical surface 26 just described by the formation andplacing of the cup 21. The cup being formed by ashort peripheral orcylindrical flange 27 at the edge of the washer or disk 28, the outer oropen edge of this flange or rim 29 is spaced, in accordance to thepreferred dimensions of the parts, from the rear wall 20 of the cavityor chamber which receives the bearing by an interval 31 slightly lessthan the short cylindrical surface 26. The motion of the cup 21 underthese circumstances corresponds but is slightly less than the extremeupward or backward motion of the outer race, which is permissiblewithout injuryto the parts. It is to be understood, however, that theexact type of bearing is not regarded as'an essential feature of theinvention in its broader conception, as herein described and claimed.

A difliculty encountered in connection with the operation andmaintenance of such tools is the tendency of the service man to mislayand leave out in reassembling various arts which he may regard asnon-essential. Vith the spring take-up, the spring is not infrequentlyomitted on reassembling, with a consequent increased play of thearmature and shaft, and a tendency to increased wear, noise, difficultyand even uncertainty of operation.

One of the objects of the present invention is to decrease the tendencyto omit the spring in assembling the tool. To this end the cup 21 isprovided with an offset or a plurality of staked edge portions 33, seeFigure 6, which project from the outer edges 29 inwardly toward thecenter of the cup and take over the base or outer coil of the spring andtend to prevent the removal of the spring from the cup without theexertion of considerable'efdial play due to wear of this bearing and theupper or rear bearing are taken up by the spring take-up described. Themanner of assembling and operation are obvious from the description anddrawings.

In the form shown in Figure l, the bearing is closed by a washer 45 onthe inside, i. e., between the armature and the bearing. This washer, inthe form shown, bears at one side against the inner race, the other sideof the washer engaging in the case of the sliding bearing a shoulder 46on the shaft and in the case of the stationary bearing the fan hub 47.

In Figure 3, two washers, one a small washer 48 which encircles theshaft just inside the end of the inner race and bearing against the sameserves to limit the motion of the balls relative to the outer race and aa second larger washer 49. which positions the inner washer 48, aresubstituted for the washers 45 in Figure 1.

I have thus described specifically and in detail a single embodiment ofmy invention in order that the nature and operation of the same may beclearly understood, however, the specific terms herein are useddescriptively rather than in a limiting sense, the scope of theinvention being defined in the claim.

What I claim as new and desire to secure by Letters Patent is:

A takeup for the ball bearings of an electric motor having a casing witha bearing housing, the takeup comprising a spiral spring, a cupenclosing and secured to the coil at the large end of the spring and astud securing the coil at the small end of the spring to the bearinghousing.

Signed by me at Baltimore, Maryland, this 22 day of June 1926.

WALTER STUMPF.

fort. The structure may be further im-' proved, and the tendency toremoval of the spring which results in its being left out when the toolis assembled, overcome, by riveting the center or forward or upper coil34.- of the spiral spring 19 to the center of the rear or top wall 35 ofthe cavity or chamber 15 in which the bearing is seated. The rivet isindicated by reference character 36, and for convenience in setting therivet the cup 21 has a central aperture 37 in the bottom to admit ariveting tool. The lower or forward bearing 40 is seated in the bushing'41 in the

